<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width,initial-scale=1.0">
    <title>Hello Vue.js</title>
</head>
<body>
    <div id="app"></div>
</body>
    <script src="https://unpkg.com/vue@next"></script>
    <script>//计时器
        Vue.createApp({
           data() {
               return{
                   counter: 0
               }
           },
           mounted(){
               setInterval(() => {
                   this.counter += 1
                }, 1000);//毫秒
               },
               template:"<div> {{counter}} </div>"
            }).mount("#app");
    </script>
</html>